Graphical analysis, simulation, and execution methods are used in modeling, design, analysis, and synthesis of engineered systems. These methods provide a visual representation of a model, for example, by representing the model as a block diagram. The visual representation provides a convenient interpretation of model components and structure. The visual representation also provides a quick intuitive notion of system behavior. The components of a block diagram can also capture a mathematical representation of the actual system being modeled.
Historically, time-based block diagram models have been used to study, design, debug, and refine dynamic systems representative of many real-world systems. A dynamic system (either natural or man-made) is a system whose response at any given time is a function of its input stimuli, its current state, and the current time. More recently, discrete event system (DES) modeling environments have been developed to allow for the design and simulation of event-driven systems. In a DES modeling environment, a system's state transitions depend on discrete incidents called events. DES models execute based upon the occurrence of events. Unlike traditional time-driven models, an event-driven model can move time forward in arbitrary increments without the need to integrate along the time intervals that each increment covers.
The occurrence of an event in a DES model may cause a generation of a function call to a function block component, a function call in code, or a function call to a function subsystem (either in the DES modeling environment or another accessible modeling environment) that are to be executed upon receipt of the function call. A delay component may be interposed between the function call generator component and the target of the function call in the model. While there are a number of mechanisms available in time-driven systems by which the amount of delay in the delay component may be dynamically adjusted during the execution of the model, corresponding mechanisms are lacking in DES model environments.